Electron tube



y 21, 1931- R. G.'BERTHOLD ET AL 1,315,229

ELECTRON TUBE Filedpe 16 ,1927 2 Sheets-Sheet 1 July 21, 1931. R. G. B'ERTHOLD ET AL 1,815,229

ELECTRON TUBE Filed Dec. 16. 1927 2 Sheets-Sheet 2 36 -F aa I I if i 5 4 3d I! a 3- a Q2 36 U Patented July 21, 1931 UNlTED STATES PATENT: OFFICE E'UDOLF G. BERTHOLD, OF BERLIN-SIEMENSSTADT, AND ROBERT STRIGE'L, OF BERLIN- CEAItLOTTENBURG, GERMANY, ASSIGNORS TO SIEMENS-SCHUCKERTWERKE AK- TIENG-ESELLSGHAFT, OF BERLIN-SIEMENSSTADT, GERMANY, A. CORPORATION OF GERY ELECTRON TUBE Application filed December 16, 1927, Serial No. 240,585, and in Germany December 17, 1926..

Our invention relates to electron tubes and Referring to Fig. 1 of the drawings, illusmore particularly to a thermionic cathode for such tubes or valves. Our invention con-- sists of a thermionic cathode which requires very little space and by means of which a high anode current can be obtained. If the electron or vacuum tube is furthermore fed with high tension anode current our improved cathode has the further advantage of great strength to withstand electrostatic forces acting upon the cathode transversely to its lon itudinal axis. Our invention is particular y suitable for heavy duty electron tubes, such as transmitting tubes in radio re] communication or tubes for controlling elecpara tric machinery.

The thermionic cathode according to our invention consists of individual strips which are arranged in such a manner that in the direction of their widths the strips stand at substantially right angles to the portion of the anode surface facing them.

A number of embodiments of our invention are illustrated in the drawings aflixed hereto and forming part of our specification.

In the drawings:

Fig. 1, represents a flat cathode in perspective view showing the general principle involved,

Fig. 2, a cathode built up of a'plurality of lel rings,

Fig. 3, the strip from which the cathode in Fig. 2 is built up,

Fig. 4, a modification of the cathode shown in Figs. 2 and 3 reinforced to be able to withstand greater electrostatic forces,

Fig. 5, a flanged cathode ring in perspective view,

Fig. 6, the flanges applied to a helical cath- Figs. 7 and 8, two further modifications of our cathode in transverse section,

Fig. 7 shows the cathode of Fig. 7 with its supporting yoke in side elevation;

Figs. 9 and 9, reinforced cathodes in side elevation and cross-sections Fig. 10, a further modified reenforced cathode in cross-sectiton and Figs. 11, 12 and 13, still further mvdifications of our improved cathode.

trating the principle involved on a flat cathode, it will be seen that the cathode conslsts of adjacent substantially parallel sections of a continuous strip ofsheet metal 2 placed on edge or at right angles to the surface of the anode 1. Since the sheet metal strips are directed towards the anode with their edges substantially the entire electron emission occurs within the spaces between, the strips from both sides of the strips and the electron emitting surfaces of the cathode are thus fully utilized provided the anode potential is sufliciently high. It is thus possible to ob tain a more powerful emission with our improved cathode than when the cathode surface consists of a solid metal sheet. A further advantage of the cathode units placed edgewise resides in the fact that when they are electrically connected in series, the ratio between the required amperage and voltage becomes more favorable than for instance in case of a closed cylinder surface which requires a very large current at very impracticably low voltages. They furthermore possess very great strength against bending strains in the direction of the anode surface. This is of particular importance in the case of high tension tubes, in View of the great electrostatic forces developed there.

Referring to Fig. 2 of the drawings, it will be observed that the glow cathode consists of individual adjacent parallel annular sheet metal strips 3 which are surrounded or enclosed by a cylindrical anode 4 of which only one half is diagrammatically shown in Fig. 2. In order to connect the individual sheet metal discs in series in a heatin circuit each of the flat rings 3 is electricafiy connected with the adjacent one by atongue 5 and the succeeding points of connection are located on diametrically opposite points of the rings. Such a glow cathode may be manufactured easily in quantities by punching a strip, as shown in Fig. 3. out of a blank. This beaded strip is then bent at the places where the connecting tongues 5 are located and folded to assume the shape shown in Fig. 2.

Should high electrostatic forces develop in the tube and comparatively great weights have to be supported the individual sheet metal'rings may be connected with one another as shown in Fig. 4-, of the drawings. These adjacent sheet metal rings are connected with one another at two opposite places by strips 6. The connections 7 to the next ring are displaced by 90 to the preceding ones.

In the design of the cathode according to Figs. 2 and 3 the heating current flows within the sheet metal rings in two branches connected in parallel, in Fig. 4 in four branches connected in parallel. In a further modification the glow cathode consists of one or a plurality of helically wound sheet metal strips, the strips being again placed edgewise against the shell of the helix or the surface of the assumed surrounding-cylindrical anode.

In orderv to stifien the edgewise placed sheet metal strip of the cathode still further against bending strains, it may be given an angular or T-shaped cross-section. The arrangement of the strip is then preferably such that the portion of the T-shaped or angular cross-section which is parallel to the surface of the anode is located on the side facing away from the anode. Fig. 5 of the drawings shows by way of example an annular sheet metal cathode according to Fig. 2 on the inner side of which is provided a sheet metal ring 8 so that a T-shaped crosssection results. Fig. 6 shows a similar from applied to a helically wound filament strip.

In Figs. 7, 7 and 8 two further modifications of our invention are shown which have the advantage of great strength to withstand electrostatic forces when the electron tubes are fed with high tension current.

Referring to Figs. 7 and 7 11 is the cylindrical anode of a high tension vacuum tube, 12 the strip-shaped glow cathode. The cathode strip running along the axis of the anode cylinder is located in the center of the anode cylinder. 13 is a yoke more clearly shown in Fig. 7 within which the cathode strip is stretched and which simultaneously serves for connecting it to the current supply so that the magnetic action of the incandescent cathode current upon the path of the electrons is compensated for the larger part. The yoke and the cathode strip are attached at their lower ends to an insulating base such as 34* in Fig. 9.

Fig. 8 of the drawings shows a design in which the anode is formed as a cylinder 11 of circular cross-section and in which a plurality of cathode strips 22 are uniformly spaced upon a circle concentric to the anode and in such a manner that their planes are located in radial planes of said cylinder. In the center is located the supporting wire 23 for the cathode strips. The power components which act upon the strips extend in the direction of their plane so that the strength of the cathode to withstand these forces is very great.

Figs. 9, 9 and 10 show two further modifications of the invention in which a mutual bracing of the cathodev strips is attained by equally spaced transverse connections distributed longitudinally of the cathode.

Referring to Figs. 9 and 9 of the drawings, 31 and 32 are the two parallel strips of a thermionic cathode the longitudinal symmetrical axis of which coincides with the axis of a cylindrical anode not shown. but assumed to be arranged similar to the manner shown in Fig. 8. The two stripsare provided with regularly spaced perforations at adjacent edges. Through any two opposite perforations is passed a wire connection 33 which prevents tilting of the two strips when subjected to strains, because these connections engage the inner edges of the strips. 34: is a conducting supporting yoke to which the upper ends of the cathode strips are attached. The yoke is mounted on an insulating base 345*, the plane through the yoke standing at right angles to the plane of the two strips. The yoke has a transverse portion 35 to which the two cathode strips 31, 32 are attached.

If it is desired to use a single central supporting post such as is shown in Fig. 8, instead of the two-armed supporting yoke, this support would be in the way of the cross connections such as 33, Fig. 9, if the number of the cathode strips is an even one. In such a case it is advisable to choose an odd number of inetal strips so that the transverse stays avoid the central support.

Fig. 10 of the drawings shows in transverse section three such cathode strips 36 connected electrically in parallel the same as strips 31, 32 in Fig. 9, and supported by a central supporting pillar 37 arranged in the central axis of anode 11. connections 38 between theindividual strips are in this case clear of the central pillar.

Figs. 11 and 12 of the drawings illustrate another modification of our invention in which the cathode consists of a single strip, a solid not glowing body being provided in the plane of the strip between the cathode and the anode and having the same potential as the cathode. In this way the electrostatic forces exerted upon the thermionic cathode are still further reduced, inasmuch as the capacity between the anode and the cathode itself is reduced thereby. The main capacity is now taken over by the solid body located between the anode and cathode. The mechanical force exerted upon the cathode material soft on account of its glowing is consequently very small.

Fig. 11 shows such a thermionic cathode in perspective view. Fig. 12 shows a transverse section on the line AB of Fig. 11, and Fig. 13 a modification of the section of the cathode shown in Fig. 12.

The transverse In Fig. 11 the cathode strip 41 islocated longitudinally in the axis of a cylindrical anode not shown. The heated portion of the cathode is fixed at its lower end in a holding device 42 and at its upper end to a yoke 43 constructed of round bars or rods. The cathode strip is located in the central plane of the yoke, as particularly clearly shown in Fig. 12. The cathode heating current flows in parallel connection through the two legs of the yoke and then through the cathode. The two legs of the yoke protect the cathode in that plane, in which the greatest electrostatic forces are exerted upon it, against said forces. The legs of the yoke are so hulky and have on the side facing away from the cathode such large surfaces, that they remain at a comparatively low temperature under the action of the heating current and the radiation of the glowing sheet metal cathode 41. .The legs of the yoke have the cross-section shown in Fig. 12. lfhey are on the inside provided with a groove 44 into which projects the free edge of the cathode strip. There are thus no exposed sharp edges on the cathode so that even when excessively high voltages develop forsome reason the permissible value of the field intensity on the cathode is not exceeded at any part.

In the modification illustrated in Fig. 13 of the drawings the legs of the yoke are solid parallel to the anode cylinder axis, said cathode consisting of a plurality of conducting flat strips, each strip having its lateral surface substantially at right angles to the surface portion of the anode immediately adjacent to it, the strip edges facing away from the anode having transverse tie elements for tieing the edges of adjacent strips together.

In testimony whereof we atlix our signatures.

RUDOLF G. BERTHOLD. ROBERT STRIGEL.

and the slots for the reception of the edge of the cathode strip are formed by sheet metal strips wrapped around the uprights of the yoke, the ends of these metal strips being located at the inside of the yoke, and forming together a gap within which the cathode ed e is located.

Tarious modifications and changes may be made without departing from the spirit and the scope of the invention, and we desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art.

We claim as our invention 1. In a thermionic tube a cylindrical anode and a thermionic cathode disposed Within said anode and extending substantially in parallel to the anode cylinder axis, said cathode consisting of at least one conducting ribbon having its lateral surface substantially at right angles to the surface portion of the anode immediately adjacent to it.

2. in a thermionic tube a cylindrical anode and a thermionic cathode disposed within said anode and extending substantially in parallel to the anode cylinder axis, said cathode consisting of a plurality of conducting fiat strips, each strip having its lateral surface substantially at right angles to the surface portion of the anode immediately adjacent to it.

- 3. In a thermionic tube a cylindrical anode and a thermionic cathode disposed within said anode and extending substantially in 

